Resistance or fuse wire



Patented Dec. 1, 1942 EDiSTATES- PATENT RESISTANCE on rose WIRE CecilSpencer Sivil, Roselle, N. J., asslgnor to Baker & Company, Inc.,Newark, N. J., a corpoi-ation of New Jersey N 0 Drawing.

Application February 11, 1941 savanna-378,376

3 Claims. (cram-is) This invention relatesfto wires suitable aselectrical resistances particularly in the ignition of explosives, suchas resistance wires or bridge wires in blasting caps, detonators and thelike.

Heretofore such resistance wires for igniting or setting off explosivesusually consisted of an alloy of platinum-iridium containing from toiridium, the alloy of 80% platinum and.

stantially of precious metals only and shall have low specific gravity,high electrical resistance and satisfactory breaking loads or tensilestrength to take the place of fuse wire of platinumiridium alloysheretofore in general use in setting off explosives, and which whilehaving char- 5 acteristics similar to those of such platinumiridiumwires shall be of considerably lower cost. It is another object ofmyinvention to produce such wires for such purposes as resistances inWheatstone bridges, resistance coils and resistance wires for use inigniting explosives, as in blasting caps, detonators or the like. Astill further object of my present invention is to provide suchresistance wires which shall be cheaper than the resistance wiresdescribed in my copending application above referred to and yet of equalquality or even superior quality.

The electrical resistance wire of my present invention consists of analloy of palladium with rhodium and iridium containing fromapproximately 60% to 95% palladium and from to 5% rhodium and iridiumcombined. Such alloys have excellent corrosion resistance and theirmelting points are in excess of the ignition point of detonatingcharges. As such alloys have, further, high electrical resistance andgreat strength they are admirably suited for such purposes as resistancewires or bridge wires in blasting caps, detonators and the like. I havefound particularly satisfactory such specific alloys aspalladium-rhodium-iridium alloys containing 80% palladium 10% rhodiumand 10% iridium,

trical resistance wire' can be obtained per ounce of alloy.

Referring to an electrical resistance wire of 80% palladium 10% rhodiumand 10% iridium,

I found, for instance, an electrical resistivity of 218 ohms/mil ft.;thus an electrical resistance wire of such alloy having a diameter of0.00138" was found to have an electrical resistance of 304 ohms/yd. anda tensile strength of 150,300 lbs.

per square inch. Compared therewith an electrical resistance wireaccording to my aforesaid copending application of an alloy of 87%palladium 10% platinum and 3% ruthenium has a resistivity of 153ohms/milft. and a wire having a diameter of 0.00135 was found to haveanelectrical resistance of 309 ohms/yd. and a tensile strength of 110,000lbs. per square inch. The

specific gravity of 'the alloy of 80% palladium 10% rhodium and 10%iridium is 12.5 and I may thus produce approximately 8150 feet of0.00138" electrical resistance wire from 1 ounce .of such alloy. Themelting point of the alloy is 1650 C. In the alloys above described'Ican replace part or all of the rhodium-iridium content with ruthenium,but I have-found that not more than 10% ruthenium should be present insuch alloys. Thus I have made experiments with for instance anelectrical resistance wire of an alloy of 95% palladium and 5%ruthenium, and an alloy of 90% palladium 5% rhodium and 5% ruthenium andfound satisfactory results as to electrical resistance and tensilestrength. The specific gravity of the alloy of 95% palladium and 5%ruthenium is 12.1 and I may thus PTO-y duce approximately 7500 feet of0.0015" electrical resistance wire from 1 ounce of such alloy.

The melting point of the alloy is 1600 C. The

particular feature of the electrical resistance wires according to thepresent invention is that is low and consequently a large footage ofelecthey are completely satisfactory without the presence of anyplatinum, whereby it is possible to take full advantage of the extremelylow price and the low specific gravity of palladium. I-

may, however,- replace palladium in the alloys with up to one-halfthereof by platinum.

What I claim is:

1. An electrical resistance wire consisting of an alloy of palladium,rhodium and iridium containing palladium from sixty percent toninety-five percent, and rhodium plus iridium from five (5) percent toforty (40) percent.

"2. An electrical resistance wire consisting of an alloy of palladium,rhodium and iridium containing from sixty (60) percent'to ninety-fivealloy.

3. electrical resistance wire for setting of! explosives consisting oran alloy composed of approximately eighty (80) percent to ninety (90)percent palladium, approximately flve (5) percent to ten (10) percentrhodium and approximately ilve (5) percent to ten (10) percent CECILSPENCER SIVIL.

5 iridium.

